Venting/pressure adjustment to aid in delivery of material into an anatomic region via a cannula

ABSTRACT

A cannulated and possibly fenestrated device for injection of material into bone can be dangerous because large, uncontrolled pressures are introduced during injection into a somewhat closed system, and material may extrude undesirably or emboli may be introduced. Methods and devices are described for providing venting of pressure upon injection of material through cannulated and possibly fenestrated screws. The first method involves a bone screw and/or anchor device that includes multiple channels to allow material to flow in through one channel and out through another channel. The second method involves a plunger that can force material into bone if advanced or lessen pressure if withdrawn. The third method involves usage of two separate screws. Material is alternately injected or withdrawn from each screw to cause material to flow from one screw to the other in a controlled way that creates a uniform or asymmetrical distribution of material as desired.

RELATED US APPLICATION DATA

U.S. Provisional application No. 61/132,041 filed on Jun. 16, 2008.

FIELD OF THE INVENTION

This invention generally relates to the medical use of screws or tubes anchored in bone or soft tissues, and particularly, to methods and systems for controlling the pressure of material delivered through the cannulations or fenestrations by venting.

BACKGROUND OF THE INVENTION

During certain medical procedures such as vertebroplasty, bone screw augmentation, or drug-delivery, it is desirable to inject foreign materials (cements, medications, etc.) into bone or other anatomic regions. For example, delivery of materials through screws with a single cannulation that may or may not include slots (fenestrations) is described in U.S. Pat. No. 6,214,012 B1, “METHOD AND APPARATUS FOR DELIVERING MATERIAL TO A DESIRED LOCATION.” However, local changes and increases in pressure at the regional injection sites can make injection through a single cannula or a radially fenestrated cannula difficult (requiring high pressures) and dangerous (can cause fat embolisms and hypertension). Apparatuses and methods that allow for venting/pressure adjustment of the injection site or region close to the delivery site are presented here, representing an improvement to this previous patent.

SUMMARY OF INVENTION

This application includes 3 related methods/devices for providing venting of pressure upon injection of material through cannulated and possibly fenestrated screws or tubes. The first method involves a device for insertion into bone or other tissue that includes at least two channels (hollow pathways, tunnels, cannulations), where one channel provides a pathway for material going into the bone/anatomic region and a second/additional channel provides a pathway for material (body fluids) going out of the bone/anatomic region at or near the site to be injected. The second method involves a plunger that can force material into bone if advanced or lessen pressure if withdrawn. The third method involves usage of two separate screws, each with a single cannulation. Material is alternately injected or withdrawn from each screw or tube to cause material to flow from one screw or tube to the other and vice versa in a controlled way that creates a uniform or asymmetrical distribution of material as desired.

BRIEF DESCRIPTION OF THE DRAWINGS

The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein:

FIG. 1 is a cross-section of a screw showing a possible configuration of channels to allow flow of material delivered into the head of the screw through a central cannulation, out into the anatomical region through distal radial fenestrations near the tip, back into the screw through radial fenestrations more proximal to the head, and then back through radially offset cannulations and up the shaft toward the screw head.

FIG. 2 is a possible configuration of a system for pumping injectate into the appropriate channel in the screw while simultaneously drawing the fluid out through the appropriate independent channel using a vacuum.

FIG. 3 demonstrates how a threaded cylinder can be inserted into a threaded channel to act as a plunger for creating positive pressure (if advanced) or suction (if withdrawn).

FIG. 4 demonstrates usage of two cannulated screws (cannulated with only a single channel) for intraoperative vertebroplasty or delivery of other material to the vertebral body.

FIG. 5 demonstrates how pilot holes may be reamed by inserting wires through one or both cannulated screws if the material through which the injectate must flow (e.g., bone) is not porous enough and the two screw tips do not communicate.

DETAILED DESCRIPTION OF THE INVENTION

The first of the three related methods involves a bone screw and/or anchor device that includes at least two channels (hollow pathways, tunnels, cannulations), where one channel provides a pathway for material going into the bone/anatomic region and a second/additional channel provides a pathway for material (body fluids) going out of the bone/anatomic region near the site to be injected.

The delivery and removal sites are close enough to each other so that the pressure at one site affects the other; that is, removal of material/fluid from the removal site should reduce the pressure at the delivery site, while injection of a material at the delivery site should increase the pressure at the removal side. By simultaneously applying positive pressure at one site and negative pressure at the other site, injection should be easier and material should flow between the two sites instead of flowing away into undesirable areas. It is also possible to not apply any additional negative pressure to the second site, but to let it act as vent (i.e., body fluids exit site for spontaneous pressure adjustement).

The channels can be straight, parallel to each other and collinear with the long axis of the bone screw/anchor device. Referring to FIG. 1, material may be delivered into the head 10 of the multi-port screw 11 through a central cannulation 12, out into the anatomical region through distal radial fenestrations near the tip 14, back into the screw through radial fenestrations more proximal to the head 16, and then back through radially offset cannulations 18 and up the shaft toward the screw head 10.

Alternately one or both channels can be curved, non-parallel to each other and at an angle with the long axis of the bone screw/anchor device. Thus, the openings can be anywhere (and strategically placed) along the bone screw/anchor device. One channel can coincide with the center long axis of the bone screw/anchor device, or both channels can be away from the center long axis.

Referring to FIG. 2, the channels for ingoing and outgoing materials in the multi-port screw 11 that has been inserted in bone or other tissue 22 can be connected to and used with an external pressure-monitoring system 19, which can be used to control the rate and amount of the injected liquid 21. Pressure on both positive pressure side and negative pressure side are monitored with a positive-pressure-side gauge 24 and a negative-pressure-side gauge 26. Controllable valves on the positive pressure side 27 and negative pressure side 28 can be controlled to adjust the flow in and out of the screw, either manually through dials or automatically through computerized control of the valves. Outflow of injectate and other waste (e.g., blood) is collected 29.

An alternative to using the controllable pressure system in FIG. 2 with a single multi-port screw is to use it with multiple cannulated needles (or a dual-channel cannula with strategically placed openings) placed into a bone screw/anchor device having a single cannula/tunnel (with or without fenestrations). The needles are inserted parallel or at an angle relative to each other, to the same or different lengths, where one needle is used to inject/deliver material, and the second (additional) needle is used to simultaneously suction material (body fluid) out of the bone/anatomic region near the site to be injected. The pressure used to remove fluid (i.e. suction) may need to be adjusted to compensate for the rate of flow of the injected material (i.e. depending on the viscosity of the injectate, etc.).

It is also possible, although probably not as well-controlled, to simply connect syringes to each channel, manually compressing one syringe while distracting the other to create positive and negative pressures.

Another option for creating suction or positive pressure in a straight channel (either in a two-screw configuration as described below or in a single screw with multiple channels) is to use a “plunger” in the channel. Such a plunger could be either a straight cylinder or a threaded cylinder within a threaded channel, as is shown in FIG. 3. FIG. 3 shows an axially cannulated and radially fenestrated screw as a cutaway view without plunger (left) or the whole screw with plunger 30 (right). After driving the screw into bone or tissue using a screwdriver that is suitable for the hex head socket in the screw head 33, material is injected into the central canal opening in the head of the screw 34. The plunger 30 is then inserted into the central canal. Threaded indentations 31 in the plunger mate with threads 32 in the wall of the cannulation, allowing the plunger to be advanced or withdrawn by rotating it clockwise or counterclockwise in the hole with a smaller screwdriver.

A different but closely related method involves the use of two cannulated (and possibly fenestrated) screws in the same piece of bone with tips in close proximity. As an example, two pedicle screws could be used during intraoperative vertebroplasty, where one screw is injecting under positive pressure while the other is withdrawing under negative pressure, allowing cement or material to flow between the screw tips. As with a single screw with multiple channels, this method prevents material from flowing outside the desired area. Referring to FIG. 4, injection begins (left image) with a single screw (left screw in this example), through which material flows and gathers near the fenestrations at the tip 40. Negative pressure is applied to the opposite screw (center image), causing material to flow toward the opposite screw tip 42 (right screw in this example) in a controlled way. If desired for a more uniform distribution of material (right image), flow through the left screw can be halted or reversed and flow through the right screw reversed (that is, material injected from the right) to build up material near the right screw tip 42.

Depending on the porosity of the bone or material between the screw tips, this two-screw technique may or may not require a pilot channel to be created so material can flow between screw tips. Referring to FIG. 5, to create a pilot hole, a reaming wire 50 may be passed through the cannulation 52 and into the bone or tissue 54. The reaming wire may be comprised of shape memory alloy such as Nitinol in a pre-coiled configuration that would allow it to angulate after exiting the tip of the screw 56 if a nonlinear pilot hole pathway is desired. Such wires could be forced into the cannulation and advanced through the straight channel, but would curl as they exited the tip. 

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 6. A device for insertion into bone or tissue comprising: a screw with a cannulation parallel to the central axis of said screw; one or more fenestrations coupled to the cannulation; and a plunger configured to be inserted in said cannulation.
 7. The device of claim 6 wherein: said cannulation is threaded and; wherein said plunger is threaded such that said plunger can be threaded within said cannulation to raise and lower said plunger.
 8. The device of claim 6 wherein: said cannulations and said fenestrations are configured such that moving said plunger in said cannulation forces an injectate to move from said cannulation to the bone or tissue in which said device is inserted.
 9. A device for insertion into bone or tissue comprising: a screw with a plurality of cannulations; and one or more fenestrations coupled to each of said plurality of cannulations.
 10. The device of claim 9 wherein: said plurality of cannulations comprise a first cannulation and a second cannulation; and said first and second cannulation are configured such that an injectate flows out through said first cannulation and flows in through said second cannulation.
 11. The device of claim 9 wherein: said plurality of cannulations are each parallel to the central axis of said screw.
 12. A method comprising: inserting a first device into a bone or tissue; inserting a second device into the bone or tissue, in close proximity to said first device; injecting injectate using said first device; and applying negative pressure using said second device.
 13. The method of claim 12 wherein said first device is a syringe.
 14. The method of claim 12 wherein said first device is a cannulated fastener.
 15. The method of claim 12 wherein said second device is a cannulated fastener.
 16. The method of claim 12 further comprising: wherein said injecting and applying steps are automatically controlled via a pressure monitoring device.
 17. The method of claim 12 wherein said first device and said second device are cannulations within a multi-cannulated device.
 18. The method of claim 12 wherein said second device is a syringe.
 19. The method of claim 12 further comprising: creating a pilot channel; wherein the location of said pilot channel is selected to create a pathway between said first device and said second device. 